The conventional receptacles are mostly composed of an upper and a lower half-shell, the lower half-shell has a seat for a conducting plate to be secured thereat, this design has an open slots which endangers to young children, and is easy to collect objects. Owing to this, a cover is introduced to cover the slot so that protecting any accidental happen. The design is shown as in FIG. 7 which is formed by an upper and a lower half-shells, and comprises a receptacle A having a base B, conducting plates A2. The base B has a plural barrels BI extending upwardly for a corresponding spring C to seat therein. The other end of the spring C seats in a sleeve D1 on the bottom end of a block D, the sleeve D1 and the barrel B1 are both formed with a slope corn D11 and a slope guide B11. Thus, the block D urged by the spring C towards a slot A1 inwardly to protect the slot A1. When pressing downward by a plug, the sleeve D1 and the barrel B1 along with the block D swing to another position which allows the slot A1 to open. Although this design protects the receptacle in one way, the structure of the receptacle requires a larger space in height and depth, if the receptacle is a thin kind, this design is not available.